Rates of colorectal cancer (CRC) are increasing in adults younger than age 50 years in both the United States and Europe, according to two recent studies.
In the first study, researchers in the U.S. used the Surveillance, Epidemiology, and End Results (SEER) database to examine trends over time in CRC incidence by stage among adults ages 40 to 49 years. The results were published by JAMA on May 21 as a research letter.
Overall, 29,532 cases of CRC were diagnosed in the study age group from 1975 to 2015. Average annual percentage changes for distant versus localized and regional stages from 1995 to 2015 were 2.9% (95% CI, 2.4% to 3.4%), 1.4% (95% CI, 1.0% to 1.7%), and 1.3% (95% CI, 0.7% to 1.9%), respectively, representing a statistically significant shift in distribution of overall stage.
From 1995 to 2015, the authors found no significant change in the proportion of localized CRC (33.7% to 33.8; P=0.90) and a decrease in the proportion of regional CRC (39.0% to 35.6%; P=0.001, respectively). However, the proportion of distant CRC increased significantly in the same time period (21.7% to 26.6%; P<0.001) and could not be explained by a decrease in unstaged cases, they noted.
The authors concluded that their results indicate increased incidence of CRC in adults ages 40 to 49 years from the 1990s through 2015 and increased diagnosis at later stages. Although the study is limited because it is based on historic staging data from nine geographic areas in the U.S., it points to a real increase in risk, the authors said. “The increasing CRC incidence and shift toward later stage at diagnosis in those aged 40 through 49 years warrant further research into the underlying causes and potential prevention methods, such as earlier screening initiation,” they wrote.
In the second study, researchers in Europe reviewed data from national and regional cancer registries on age-related CRC incidence and mortality between 1990 and 2016. In that time period, 187,918 adults ages 20 to 49 years from 20 European countries were diagnosed with CRC. The study results were published May 16 by Gut.
The researchers found that CRC incidence increased 7.9% per year on average in adults ages 20 to 49 years from 2004 to 2016. Among those ages 30 to 39 years of age, the increase was 4.9% per year from 2005 to 2016, and among those ages 40 to 49 years, the increase was 1.6% per year from 2004 to 2016. Increases began earliest in patients ages 20 to 29 years and began 10 to 20 years later in patients ages 30 to 39 years, consistent with an age-cohort phenomenon, the authors noted.
The researchers pointed out that they did not include data from all countries in the European Union and that not all countries involved in the study could provide data from all regions or for the entire 25-year time frame, among other limitations. However, they concluded that based on their data, CRC incidence is increasing among adults ages 20 to 49 years of age in Europe.
“If this trend continues, screening guidelines may need to be reconsidered,” the researchers wrote. “Until the underlying cause of this trend is clarified, it would be commendable to raise clinicians' awareness and identify factors possibly associated with this trend.”